The federal investigation into Gov. James E. McGreevey's accusation that a former aide tried to extort him by threatening to reveal their extramarital affair is now focusing on a strange, last-minute offer to keep the matter secret if the governor agreed to approve a plan for a new medical school in New Jersey, according to three people involved in the inquiry.

Just 10 minutes before Mr. McGreevey was scheduled to announce his resignation last Thursday, a member of his inner circle received a telephone call from a lawyer who identified himself as an intermediary for Golan Cipel, the aide who was threatening to sue the governor for sexual assault and harassment.

The caller, Timothy Saia, reportedly said that Mr. Cipel would agree not to go public with his charges if Mr. McGreevey granted a charter to Touro College, a New York City institution that has been unsuccessfully seeking to open a medical facility in New Jersey for months...

In its effort to get approval of a charter, Touro was also represented by former Senator Robert G. Torricelli, who now works as a political consultant...